We will examine the replication of chromatin in an in vitro system, using HeLa cell nuclei. We will characterize in detail the structure of newly replicated chromatin; i.e., initial submit size, subunit heterogeneity, and extended DNAase I ladder pattern. Soluble replication factors will be characterized for their effect on the replication process in vitro. We are currently studying factors which stimulate the rate and extend of DNA synthesis, affect the conformation of the nucleosome during replication, and mediate the processes of gap-filling and ligation on nucleosome-associated Okazaki fragments.